This regulation does not apply to fuel contained in the fuel system of the transporting vehicle, or in the fuel systems of vehicles and equipment being towed or carried. Flames used for heating vehicles or loads shall be extinguished before the vehicle enters any tunnel or its approaches. The following classes of hazardous materials are prohibited from being transported through any tunnel or its approaches, as indicated: Forbidden materials and forbidden explosives are prohibited; Class 1 explosives are prohibited; Class 2, division 2.1 flammable gas is prohibited, with exceptions for propane, LPG, CNG, LNG, and other flammable compressed gas in U.S.D.O.T. approved containers, in quantities not to exceed 10 pounds gross weight per container, and 100 pounds gross weight per vehicle; Class 2, Division 2.2 nonflammable compressed gas is prohibited, with the following exceptions: Argon, compressed, Argon, refrigerated liquid, Carbon dioxide, refrigerated liquid, Compressed air in containers only, although this is prohibited if in tank vehicles, Helium, compressed, Nitrogen, refrigerated liquid, Nitrogen, compressed, or Oxygen in containers only, although this is prohibited if in tank vehicles; Class 2, division 2.3 poisonous gas is prohibited; Class 3, flammable liquid is prohibited, with exceptions for motor fuel and petroleum-based products in U.S.D.O.T. or Underwriter's Laboratory approved containers in total quantities not to exceed 5 gallons per container and 20 gallons per vehicle; Class 3, combustible liquid is permitted, with the exception of formaldehyde solutions which are prohibited; Class 4, division 4.1 flammable solid is prohibited, with the exception of fusees in quantities not to exceed 100 pounds per vehicle; Class 4, division 4.2 spontaneously combustible materials are prohibited; Class 4, division 4.3 dangerous-when-wet materials are prohibited; Class 5, division 5.1 oxidizers are prohibited; Class 5, division 5.2 organic peroxides are prohibited; Class 6, division 6.1 poisonous materials are prohibited, with the following exceptions: Arsenic in any form or compound, Tree-killing or weed-killing liquid compounds, Cyanide of potassium, Cyanide of sodium, Drugs, chemicals, medicines, or cosmetics, not otherwise specified, liquid or solid, Insecticides, dry, or Motor fuel antiknock compound; Class 6, division 6.2 infectious substances are prohibited; Class 7, radioactive materials are prohibited, with the exception of manufactured articles such as instrument or clock dials, electronic tubes of which radioactive materials are a component part, watches, X-ray machines, smoke detectors, etc; Class 8, corrosive materials are prohibited, except batteries; Class 9, miscellaneous hazardous material is prohibited, with the exception of oils, N.O.S., with a flashpoint not less than 93°C (200°F); and Other regulated material: ORM-D is permitted. Tank vehicles which are empty, or which have a residue of not more than 50 gallons, or vehicles transporting empty containers are prohibited from entering any tunnel if they previously transported a prohibited hazardous material, with the following exceptions: Tank vehicles or containers that have been sufficiently cleaned of residue and purged of vapor to remove any potential hazard; Tank vehicles or containers that have been reloaded with a material not classified as a hazardous material; Tank vehicles or containers whose previous cargo was: A Class 3 combustible liquid, A Class 8 corrosive material, A Class 5 oxidizer, or A Class 5 organic peroxide; or Completely empty containers whose previous cargo was a Class 3 flammable liquid. Tank vehicles used to transport Class 3 flammable liquids, even if empty, are prohibited from entering any tunnel. Notwithstanding the restrictions in §§A—E of this regulation, vehicles transporting hazardous materials prohibited from entering any tunnel may use: The Baltimore Harbor Tunnel Thruway from the Child Street entrance ramp in a southbound direction only; I-95 northbound to the Key Highway exit ramp south of the Fort McHenry Tunnel, and from the Keith Avenue entrance ramp north of the Fort McHenry Tunnel; or I-95 southbound to the Keith Avenue exit ramp north of the Fort McHenry Tunnel and from the Key Highway entrance ramp south of the Fort McHenry tunnel.